Development of fluorescent molecules and their application are indispensable techniques for the analysis of a variety of biological phenomena. During the past few decades, a number of fluorescent small molecules have been developed as reporters and chemosensors for use in biological analyses, which typically are elaborately designed to selectively detect a target substance or conjugated to biomolecules1. These fluorescent molecules employ an increase or decrease in their emission intensity in response to the surrounding medium or through specific molecular recognition events. Due to their simplicity and high sensitivity, fluorescent sensors have been widely utilized as popular tools for chemical, biological and medical applications. The most general strategy for fluorescent sensor design is to combine fluorescence dye molecules with designed receptors for specific analytes, expecting that the recognition event between receptor and analyte will lead to a fluorescence property change of the dye moiety. Although many fluorescent sensors have been successfully developed through this approach, each individual development requires a major effort in both the design and synthesis of the sensors. Also, the sensor's scope of application is limited to the selected specific analytes that the sensor was rationally designed for, so-called Analyte Directed Sensors. Combinatorial dye library synthesis offers one of the most promising alternatives as Diversity Directed Sensors, once an efficient synthetic route can be developed for a diverse set of dyes.
Neural stem cells (NSC) generate the nervous system, promote neuronal plasticity and repair damage throughout life by self-renewing and differentiating into neurons and glia2,3. Beneficial effects of NSC engraftment into the affected brain areas in several brain diseases have been demonstrated by animal experiments4,5. NSC also has great potential for drug screening and efficacy testing significantly reducing the time and efforts needed in drug discovery. The conventional methods for the isolation and characterization of NSC depend on their behavior in a defined culture medium such as neurosphere formation and immunodetection of marker molecules. These methods, however, are time-dependent and involve the use of antibodies which may render the cells unsuitable for further experimental and therapeutic applications. Therefore, a need exists to develop novel chemical compounds that are useful for detection of neural stem cells.